The present invention generally relates to counter pressure garments and, more particularly, to counter pressure garments, such as gloves, that can be used in low pressure environments.
Blood pressure in a human subject""s body is slightly higher than the breathing pressure. In a standard atmospheric environment this breathing pressure is equal to the external gas pressure on the skin. In environments having very small or no gas pressure, such as the vacuum of the space or very high altitude, breathing is often enhanced or enabled only by positive pressure gas supply. In these cases, a subject""s circulatory balance and respiration are of great concern.
The human body is covered with a soft tissue layer. The pressure of this layer is always equal to the external gas pressure on the skin. In normal atmospheric pressure, the tissue pressure in this layer matches the blood pressure of the circulatory system. In a low pressure environment with positive pressure breathing, however, since the pressure over the tissue layer is lower, the circulating blood may rush into the tissue layer and pool. If no preventive step has been taken, the veins, particularly the capillary ones in the tissue layer, are engorged with blood. As venous engorgement continues, measurable amounts of excess fluid can be forced through the capillary walls and accumulate in the tissue layer. The accumulation of fluid can result in formation of petechiae or edema and a decrease in the circulating blood.
In such low pressure environments, a counter pressure must be applied over the soft tissue layer to prevent the aforementioned problems. Usually, a counter pressure suit is employed to provide the necessary counter pressure on the tissue layer. In the context of outer space, one such suit is a full pressure suit. It is a gas filled pressure suit that is gas tight. The counter pressure in a full pressure suit is created with high pressure oxygen supplied into the suit. Thus, the gas pressure on the skin is in balance with the breathing pressure. Typically, these suits are made of a rigid but pressure restraining outer garment.
Another type of suit is generally referred to as a partial pressure suit, used, for example, in high-altitude fighter airplanes. In a partial pressure suit, an elastic or inelastic outer garment typically covers bladders that are filled with gas. The bladders with the garment can apply a constant counter pressure over the tissue. Partial pressure suits have their advantages. For example, if the partial pressure suit is developed with elastic material, the elastic material itself can provide counter pressure to the body. The partial pressure suits tend to be less bulky and thereby increasing mobility.
One important drawback with the partial pressure suit is that in order to apply a counter pressure over a body part, that body part must be perfectly circular in shape. But the body is not circular, and instead ovate, ellipsoidal and irregular. In this context, among other body parts, hands present an exceptional difficulty. A hand has a combination of concave, convex and circular areas as well as many joints and muscular areas that change shape during contraction and relaxation.
Specifically, the hand includes a palm having five fingers. The palm has a palmar surface that contacts an object being grasped, and a dorsal surface that is the upper surface of the hand. The palmar and dorsal surfaces are defined by the bones and soft tissue covering the bones. These bones consist of five metacarpals that extend from the wrist up to the base of the fingers or so called palmar knuckles. These five metacarpals are dished, creating a metacarpal arc in the central part of the palm. At the distal ends of the metacarpals, the fingers are attached. The index, middle, ring and little fingers each have three cylindrical phalanges, with the phalanx attached to the corresponding metacarpal being the proximal phalanx, the next phalanx being the middle and the fingertips being the distal phalanx. The thumb has only two cylindrical phalanges, a proximal and distal.
Due to its importance and its complex shape, the palm has been a center of attention in various research studies. It has been observed that if used for counter pressure purposes, the elastic material of a counter pressure glove tend to primarily press the outer edge of the palm and leaves the dorsal and palmar surfaces without adequate pressure. In an effort to address this problem, bladders with various shapes are placed on the palmar and dorsal surfaces before donning the glove. However, even such conventional bladders are large and stiff, and they are not able to eliminate fluid accumulation in the soft tissue in the metacarpal area. Their large size and stiffness decrease dexterity, tactility, and mobility. Further, their size and stiffness make donning and doffing of the elastic glove more difficult. More importantly, the size and the stiffness of the bladders fatigue the elastic glove during donning and doffing resulting in a defective glove.
As can be seen, there is a need for an improved counter pressure glove that provides adequate counter pressure to the palm of a hand and is easy to don and doff as well as increase dexterity, tactility, and mobility of the hand.
A mechanical counter pressure glove system comprises a slip layer or base glove defining an internal volume for receiving a hand of a wearer and a power layer or pressure inducing glove. The pressure inducing glove is donned on the base glove so as to apply a mechanical pressure on the hand. The low friction material of the base glove facilitates donning of the pressure inducing glove.
A donning-enabling garment for use in a mechanical counter pressure glove system comprises a seamless body of a low friction material defining an internal volume for receiving a hand of a wearer. The seamless body is knitted from a yarn that is made of the low friction material. The seamless body defines a finger portion for receiving the fingers and the thumb, a palm portion for receiving the palm, and a wrist portion for receiving the wrist of the hand.